MUSCL THINC right-state reconstruction uses already-overwritten left-state values

[sbryngelson]

Bug

In `src/simulation/m_muscl.fpp`, the THINC interface reconstruction computes the left-state first, overwriting the density ratio values. The subsequent right-state computation reads these already-overwritten values instead of the original ones.

File: `src/simulation/m_muscl.fpp`, lines 285-301

Impact: Right-state THINC reconstruction uses contaminated density ratios from the left-state computation. Currently masked by algebraic coincidence in simple cases, but produces wrong results when left and right densities differ significantly.

Severity: High — silent corruption of MUSCL-THINC interface reconstruction.

[sbryngelson]

Fix: #1179

[sbryngelson]

fix #1303

[sbryngelson]

Maybe addressed by #1303 ? @wilfonba

[sbryngelson]

Addressed by #1303. The compression logic was moved from m_muscl.fpp into the new m_thinc.fpp module, where density ratios rho_b and rho_e are saved from the original cell-center volume fraction before any overwrites, and both left and right reconstructions use those saved values. The overwrite-then-read bug is gone.